Fan array control system

ABSTRACT

A fan array fan section in an air-handling system includes a plurality of fan units arranged in a fan array and positioned within an air-handling compartment. One preferred embodiment may include an array controller programmed to operate the plurality of fan units at peak efficiency by computing the power consumed in various configurations and selecting the configuration requiring minimum power to operate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application61/255,364 filed Oct. 27, 2009, which is hereby incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

The present invention is directed to a fan array fan section utilized inan air-handling system.

Air-handling systems (also referred to as an air handler) havetraditionally been used to condition buildings or rooms (hereinafterreferred to as “structures”). An air-handling system is defined as astructure that includes components designed to work-together in order tocondition air as part of the primary system for ventilation ofstructures. The air-handling system may contain components such ascooling coils, heating coils, filters, humidifiers, fans, soundattenuators, controls, and other devices functioning to meet the needsof the structures. The air-handling system may be manufactured in afactory and brought to the structure to be installed or it may be builton site using the necessary devices to meet the functioning needs of thestructure. The air-handling compartment 102 of the air-handling systemincludes the inlet plenum 112 prior to the fan inlet cone 104 and thedischarge plenum 110. Within the-air-handling compartment 102 issituated the fan unit 100 (shown in FIGS. 1 and 2 as an inlet cone 104,a fan 106, and a motor 108), fan frame, and any appurtenance associatedwith the function of the fan (e.g. dampers, controls, settling means,and associated cabinetry). Within the fan 106 is a fan wheel (not shown)having at least one blade. The fan wheel has a fan wheel diameter thatis measured from one side of the outer periphery of the fan wheel to theopposite side of the outer periphery of the fan wheel. The dimensions ofthe handling compartment 102 such as height, width, and airway lengthare determined by consulting fan manufacturers data for the type of fanselected.

FIG. 1 shows an exemplary prior art air-handling system having a singlefan unit 100 housed in an air-handling compartment 102. For exemplarypurposes, the fan unit 100 is shown having, an inlet cone 104, a fan106, and a motor 108. Larger structures, structures requiring greaterair volume, or structures requiring higher or lower temperatures havegenerally needed a larger fan unit 100 and a generally correspondinglylarger air-handling compartment 102.

As shown in FIG. 1, an air-handling compartment 102 is substantiallydivided into a discharge plenum 110 and an inlet plenum 112. Thecombined discharge plenum 110 and the inlet plenum 112 can be referredto as the airway path 120. The fan unit 100 may be situated in thedischarge plenum 110 as shown), the inlet plenum 112, or partiallywithin the inlet plenum 112 and partially within the discharge plenum110. The portion of the airway path 120 in which the fan unit 100 ispositioned may be generically referred to as the “fan section”(indicated by reference numeral 114). The size of the inlet cone 104,the size of the fan 106, the size the motor 108, and the size of the fanframe (not shown) at least partially determine the length of the airwaypath 120. Filter banks 122 and/or cooling coils (not shown) may be-addedto the system either upstream or downstream of the fan units 100.

For example, a first exemplary structure requiring 50,000 cubic feet perminute of air flow at six (6) inches water gage pressure would generallyrequire a prior art air-handling compartment 102 large enough to house a55 inch impeller, a 100 horsepower motor, and supporting framework. Theprior art air-handling compartment 102, in turn would be approximately92 inches high by 114 to 147 inches wide and 106 to 112 inches long. Theminimum length of the air-handling compartment 102 and/or airway path120 would be dictated by published manufacturers data for a given fantype, motor size, and application. Prior art cabinet sizing guides showexemplary rules for configuring an air-handling compartment 102. Theserules are based on optimization, regulations, and experimentation.

For example, a second exemplary structure includes a recirculation airhandler used in semiconductor and pharmaceutical clean rooms requiring26,000 cubic feet per minute at two (2) inches-water gage pressure. Thisstructure would generally require a prior art air-handling system with aair-handling compartment 102 large enough to house a 44 inch impeller, a25 horsepower motor, and supporting framework. The prior artair-handling compartment 102, in turn would be approximately 78 incheshigh by 99 inches wide and 94 to 100 inches long. The minimum length ofthe air-handling compartment 102 and/or airway path 120 would bedictated by published manufacturers data for a given fan type, motorsize and application. Prior art cabinet sizing guides show exemplaryrules for configuring an air-handling compartment 102. These rules arebased on optimization, regulations, and experimentation.

These prior art air-handling systems have many problems including thefollowing exemplary problems:

Because real estate (e.g. structure space) is extremely expensive, thelarger size of the air-handling compartment 102 is extremelyundesirable.

The single fan units 100 are expensive to produce and are generallycustom produced for each job.

Single fan units 100 are expensive to operate.

Single fan units 100 are inefficient in that they only have optimal orpeak efficiency over a small portion of their operating range.

If a single fan unit 100 breaks down, there is no air conditioning atall.

The low frequency sound of the large fan unit 100 is hard to attenuate.

The high mass and turbulence of the large fan unit 100 can causeundesirable vibration.

Height restrictions have necessitated the use of air-handling systemsbuilt with two fan units 100 arranged horizontally adjacent to eachother. It should be noted, however, that a good engineering practice isto design air handler cabinets and discharge plenums 110 to besymmetrical to facilitate more uniform air flow across the width andheight of the cabinet. Twin fan units 100 have been utilized where thereis a height restriction and the unit is designed with a high aspectratio to accommodate the desired flow rate. As shown in the Greenheck“Installation Operating and Maintenance Manual,” if side-by-sideinstallation was contemplated, there were specific instructions toarrange the fans such that there was at least one fan wheel diameterspacing between the fan wheels and at least one-half a fan wheeldiameter between the fan and the walls or ceilings. The Greenheckreference even specifically states that arrangements “with less spacingwill experience performance losses.” Normally, the air-handling systemand air-handling compartment 102 are designed for a uniform velocitygradient of 500 feet per minute velocity in the direction of air flow.The two fan unit 100 air-handling systems, however, still substantiallysuffered from the problems of the single unit embodiments. There was norecognition of advantages by increasing the number of fan units 100 fromone to two. Further, the two fan unit 100 section exhibits a non-uniformvelocity gradient in the region following the fan unit 100 that createsuneven air flow across filters, coils, and sound attenuators.

It should be noted that electrical devices have taken advantage ofmultiple fan cooling systems. For example, U.S. Pat. No. 6,414,845 toBonet uses a multiple-fan modular cooling component for installation inmultiple component-bay electronic devices. Although some of theadvantages realized, in the Bonet system would be realized in thepresent system, there are significant differences. For example, theBonet system is designed to facilitate electronic component cooling bydirecting the output from each fan to a specific device or area. TheBonet system would not work to direct air flow to all devices in thedirection of general air flow. Other patents such as U.S. Pat. No.4,767,262 to Simon and U.S. Pat. No. 6,388,880 to El-Ghobashy et al.teach fan arrays for use with electronics.

Even in the computer and machine industries, however, operating fans inparallel is taught against as not providing the desired results exceptin low system resistance situations where fans operate in near freedelivery. For example, Sunon Group has a web page in which they show twoaxial fans operating in parallel, but specifically state that if “theparallel fans are applied to the higher system resistance that enclosurehas, . . . less increase in flow results with parallel fan operation.”Similar examples of teaching against using fans in parallel are found inan article accessible from HighBeam Research's library(stati.highbearm.com) and an article by Ian McLeod accessible at(papstplc.com).

BRIEF DESCRIPTION OF THE INVENTION

The present invention is directed to a fan array fan, section in anair-handling system that includes a plurality of fan units arranged in afan array and positioned within an air-handling, compartment. Onepreferred embodiment may include an array controller programmed tooperate the plurality of fan units at peak efficiency. The plurality offan units may be arranged in a true array configuration, a spacedpattern array configuration, a checker board array configuration, rowsslightly offset array configuration, columns slightly offset arrayconfiguration, or a staggered array configuration.

The foregoing and other objectives, features, and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention, taken in conjunctionwith the accompanying drawings.

The foregoing and other objectives, features, and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention, taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side view of an exemplary prior art air-handling systemhaving a single large fan unit within an air-handling compartment.

FIG. 1B is a perspective view of an exemplary prior art large fan unit.

FIG. 2A is a side view of an air handling system of the prior art havinga plurality of small fan units within an air-handling compartment.

FIG. 2B is a perspective view of a prior art fan array fan section.

FIG. 3 is a side view of an exemplary fan array fan section in anair-handling system of the present invention having a plurality of smallfan units within an air-handling compartment.

FIG. 4 is a plan or elevation view of a 4×6 exemplary fan array fansection in an air-handling system of the present invention having aplurality of small fan units within an air-handling compartment.

FIG. 5 is a plan or elevation view of a 5×5 exemplary fan array fansection in an air-handling system of the present invention having aplurality of small fan units within an air-handling compartment.

FIG. 6 is a plan or elevation view of a 3×4 exemplary fan array fansection in an air-handling system of the present invention having aplurality of small fan units within an air-handling compartment.

FIG. 7 is a plan or elevation view of a 3×3 exemplary fan array fansection in an air-handling system of the present invention having aplurality of small fan units within an air-handling compartment.

FIG. 8 is a plan or elevation view of a 3×1 exemplary fan array fansection in an air-handling system of the present invention having aplurality of small fan units within an air-handling compartment.

FIG. 9 is a plan or elevation view of an alternative exemplary fan arrayfan section in an air-handling system of the present invention in whicha plurality of small fan units are arranged in a spaced pattern arraywithin an air-handling compartment.

FIG. 10 is a plan or elevation view of an alternative exemplary fanarray fan section in an air-handling system of the present invention inwhich a plurality of small fan units are arranged in a checker boardarray within an air-handling compartment.

FIG. 11 is a plan or elevation view of an alternative exemplary fanarray fan section in an air-handling system of the present invention inwhich a plurality of small fan units are arranged in rows slightlyoffset array within an air-handling compartment.

FIG. 12 is a plan or elevation view of an alternative exemplary fanarray fan section in an air-handling system of the present invention inwhich a plurality of small fan units are arranged in columns slightlyoffset array within an air-handling compartment.

FIG. 13 is a plan or elevation view of a 5×5 exemplary fan array fansection in an air-handling system of the present invention running at52% capacity by turning a portion of the fans on and a portion of thefans off.

FIG. 14 is a-plan or elevation view of a 5×5 exemplary fan array fansection in an air-handling system of the present invention running at32% capacity by turning a portion of the fans on and a portion of thefans off.

FIG. 15 is a side view of an alternative exemplary fan array fan sectionin an air-handling system of the present invention having a plurality ofstaggered small fan units within, an air-handling compartment.

FIG. 16 is a perspective view of an exemplary fan array using a gridsystem into which fan units are mounted.

FIG. 17 shows airflow between the two panels which representacoustically insulated surfaces and sound attenuation layers.

FIG. 18 shows an embodiment in which a fiberglass core has both sideslayered with open cell foam.

FIG. 19A shows an embodiment in which a fiberglass core has an open cellfoam layered on one side of the fiberglass core.

FIG. 19B shows an embodiment in which an open cell structure of the opencell foam allows portions of the open cell foam to protrude fromopenings defined in the perforated rigid facing.

FIG. 20 shows an exemplary graph of two materials that provide differenttypes of sound absorption over a range of frequencies.

FIG. 21 shows a front view of the open cell structure of FIG. 19B thatallows portions of the open cell foam to protrude from openings definedin the perforated rigid facing.

FIG. 22 shows an exemplary air handler with a bottom section using theembodiment of FIG. 19A.

FIG. 23 shows an embodiment in which the entire insulation board isreplaced with an uncoated open cell foam pad.

FIG. 24 shows an exemplary insulated grid system or modular unit systemwith interior surfaces made from acoustically absorptive material thatreduces sound wave reaction as the sound waves travel through theinsulation surfaces.

FIG. 25 shows the system of FIG. 24 when the central fan unit isloudest.

FIG. 26 shows the system of FIG. 24 when the first side fan unit isloudest.

FIG. 27 shows the system of FIG. 24 and a first side fan unit and asecond side fan unit with their respective sound waves.

FIG. 28 shows the system of FIG. 24 and emphasizes a first corner fanunit and its wave pattern.

FIG. 29 shows the system of FIG. 24 and emphasizes first and secondcorner fan units and their respective wave pattern.

FIG. 30 graphically shows a principle of an embodiment in that, as thesound waves A and B interact, there is a degree of wave cancellation.

FIG. 31 shows an embodiment using either a grid system or modular unitsusing separate structure (not shown) for interlocking the fan units.

FIG. 32 shows an array of dampeners that may be positioned either infront of or behind the fan units to at least partially prevent backdrafts.

FIG. 33 illustrates an algorithm for operating a fan array in accordancewith an embodiment.

FIG. 34 illustrates an algorithm for operating a fan array in accordancewith an embodiment.

FIG. 35 illustrates an algorithm for operating a fan array in accordancewith an embodiment.

FIG. 36 illustrates an algorithm for operating a fan array in accordancewith an embodiment.

FIG. 37 illustrates a local fan array control system formed inaccordance with an embodiment.

FIG. 38 illustrates a distributed fan array control system formed inaccordance with an embodiment.

FIG. 39 illustrates a block diagram of a system formed in accordancewith an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a fan array fan section in anair-handling system. As shown in FIGS. 3-12, the fan array fan sectionin the air-handling system uses a plurality of individual single fanunits 200. In one preferred embodiment, the fan units 200 are arrangedin a true array (FIGS. 4-8), but alternative embodiments may include,for example, alternative arrangements such as in a spaced pattern (FIG.9), a checker board (FIG. 10), rows slightly offset (FIG. 11), orcolumns slightly offset (FIG. 12). As the present invention could beimplemented with true arrays and/or alternative arrays, the term “array”is meant to be comprehensive.

The fan units 200 in the fan array of the present invention may bespaced as little as 20% of a fan wheel diameter. Optimum operatingconditions for a closely arranged array may be found, at distances aslow as 30% to 60% of a fan wheel diameter. By closely spacing the fanunits 200, more air may be moved in a smaller space. For example, if thefan wheels of the fan units 200 have a 20 inch fan wheel diameter, onlya 4 inch space (20%) is needed between the outer periphery of one fanwheel and the outer periphery of the adjacent fan wheel (or a 2 inchspace between the outer periphery of a fan wheel and an the adjacentwall or ceiling).

By using smaller fan units 200 it is possible to support the fan units200 with less intrusive structure (fan frame). This can be compared tothe large fan frame that supports prior art fan units 100 and functionsas a base. This large fan frame must be large and sturdy enough tosupport the entire weight of the prior art fan units 100. Because oftheir size and position, the known fan frames cause interference withair flow. In the preferred embodiment, therefore, the fan units 200 ofthe fan array may be supported by a frame that supports the motors 108with a minimum restriction to air flow.

As mentioned in the Background, others have tried using side-by-sideinstallation of two fan units 100 arranged horizontally adjacent to eachother within an air-handling system. As is also mentioned in theBackground, fan arrays have been used in electronic and computerassemblies. However, in the air-handling system industry, it has alwaysbeen held that there must be significant spacing between thehorizontally arranged fan wheels and that arrangements with less spacingwill experience performance losses. A single large fan moves all the airin a cabinet. Using two of the same or slightly smaller fans caused theair produced by one fan to interfere with the air produced by the otherfan. To alleviate the interference problem, the fans had to be spacedwithin certain guidelines—generally providing a clear space between thefans of a distance of at least one wheel diameter (and a half a wheeldiameter to an adjacent wall). Applying this logic, it would not havemade sense to add more fans. And even if additional fans had been added,the spacing would have continued to be at least one wheel diameterbetween fans. Further, in the air-handling system industry, verticallystacking fan units would have been unthinkable because the means forsecuring the fan units would not have been conducive to such stacking(they are designed to be positioned on the floor only).

It should be noted that the plenum fan is the preferred fan unit 200 ofthe present invention. In particular, the APF-121, APF-141, APF-161, andAPF-181 plenum fans (particularly the fan wheel and the fan cone)produced by Twin City Fan Companies, Ltd. of Minneapolis, Minn., U.S.has been found to work well. The reason that plenum fans work best isthat they do not produce points of high velocity such as those producedby axial fans and housed centrifugal fans and large plenum fans.Alternative embodiments use known fan units or fan units yet to bedeveloped that will not produce high velocity gradients in the directionof air flow. Still other embodiments, albeit less efficient, use fanunits such as axial fans and/or centrifugal housed fans that have pointsof high velocity in the direction of air flow.

In the preferred embodiment, each of the tan units 200 in the fan arrayfan section in the air-handling system is controlled by an arraycontroller 300 (FIGS. 13 and 14). In one preferred embodiment, the arraycontroller 300 may be programmed to operate the fan units 200 at peakefficiency. In this peak efficiency embodiment, rather than running allof the fan units 200 at a reduced efficiency, the array controller 300turns off certain fan units 200 and runs the remaining fan units 200 atpeak efficiency. In an alternative embodiment, the fan units 200 couldall run at the same power level (e.g. efficiency and/or flow rate) ofoperation.

Another advantage of the present invention is that the array controller300 (which may be a variable frequency drive (VFD)) used for controllingfan speed and thus flow rate and pressure, could be sized for the actualbrake horsepower of the fan array fan section in the air-handlingsystem. Since efficiency of the fan wall array can be optimized over awide range of flow rates and pressures, the actual operating powerconsumed by the fan array is substantially less than the actualoperating power consumed by the comparable prior art air-handlingsystems and the array controller's power could be reduced accordingly.The array controller 300 could be sized to the actual power consumptionof the fan array where as the controller (which may have been a variablefrequency drive) in a traditional design would be sized to the maximumnameplate rating of the motor per Electrical Code requirements. Anexample of a prior art fan design supplying 50,000 cubic feet per minuteof air at 2.5 inches pressure, would require a 50 horsepower motor and50 horsepower controller. The new invention will preferably use an arrayof fourteen 2 horsepower motors and a 30 horsepower array controller300.

This invention solves many of the problems of the prior art air-handlingsystems including, but not limited to real estate, reduced productioncosts, reduced operating expenses, increased efficiency, improved airflow uniformity, redundancy, sound attenuation advantages, and reducedvibration.

Controllability

As mentioned, preferably each of the fan units 200 in the fan array fansection in the air-handling system is controlled by an array controller300 (FIGS. 13 and 14) that may be programmed to operate the fan units200 at peak efficiency. In this peak efficiency embodiment, rather thanrunning all of the fan units 200 at a reduced efficiency, the arraycontroller 300 is able to turn off certain fan units 200 and run theremaining fan units 200 at peak efficiency. Preferably, the arraycontroller 300 is able to control fan units 200 individually, inpredetermined groupings, and/or as a group as a whole.

For example, in the 5×5 fan array such as that shown in FIGS. 5, 13, and14, a person desiring to control the array may select desired airvolume, a level of air flow, a pattern of air flow, and/or how many fanunits 200 to operate. Turning first to air volume, each fan unit 200 ina 5×5 array contributes 4% of the total air. In variable air volumesystems, which is what most structures have, only the number of fanunits 200 required to meet the demand would operate. A control system(that may include the array controller 300) would be used to take fanunits 200 on line (an “ON” fan unit 200) and off line (an “OFF” fan unit200) individually. This ability to turn fan units 200 on and off couldeffectively eliminate the need for a variable frequency drive.Similarly, each fan unit 200 in a 5×5 array uses 4% of the total powerand produces 4% of the level of air flow, Using a control system to takefan units 200 on line and off line allows a user to control power usageand/or air flow. The pattern of air flow can also be controlled if thatwould be desirable. For example, depending on the system it is possibleto create a pattern of air flow only around the edges of a cabinet orair only at the top. Finally, individual fan units 200 may be taken online and off line. This controllability may be advantageous if one ormore fan units 200 are not working properly, need to be maintained (e.g.needs general service), and/or need to be replaced. The problematicindividual fan units 200 may be taken offline while the remainder of thesystem remains fully functional. Once the individual fan units 200 areready for use, they may be brought back on line.

A further advantage to taking fan units 200 on and off line occurs whenbuilding or structure control systems require low volumes of air atrelatively high pressures. In this case, the fan units 200 could bemodulated to produce a stable operating point and eliminate the surgeeffects that sometimes plague structure owners and maintenance staff.The surge effect is where the system pressure is too high for the fanspeed at a given volume and the fan unit 200 has a tendency to go intostall.

Examples of controllability are shown in FIGS. 13 and 14. In the fanarray fan section in the air-handling system shown in FIG. 13, the arraycontroller 300 alternates “ON” fan units 200 and “OFF” fan units 200 ina first exemplary pattern as shown so that the entire system is set tooperate at 52% of the maximum rated air flow but only consumes 32% offull rated power. These numbers are based on exemplary typical fanoperations in a structure. FIG. 14 shows the fan array fan section inthe air-handling system set to operate at 32% of the maximum rated airflow but only consumes 17% of full rated power. These numbers are basedon exemplary typical fan operations in a structure. In this embodiment,the array controller 300 creates a second exemplary pattern of “OFF” fanunits 200 and “ON” fan units 200 as shown.

Real Estate

The fan array fan section in the air-handling section 220 of the presentinvention preferably uses (60% to 80%) less real estate than prior artdischarge plenums 120 (with the hundred series number being prior art asshown in FIG. 1 and the two hundred series number being the presentinvention as shown in FIG. 3) in air-handling systems. Comparing theprior art (FIG. 1) and the present invention (FIG. 3) shows a graphicalrepresentation of this shortening of the airway path 120, 220. There aremany reasons that using multiple smaller fan units 200 can reduce thelength of the airway path 120, 220. For example, reducing the size ofthe fan unit 100, 200 and motor 108, 208 reduces the length of thedischarge plenum 110, 210. Similarly, reducing the size of the inletcone 104, 204 reduces the length of the inlet plenum 112, 212. Thelength of the discharge plenum 110, 210 can also be reduced because airfrom the fan array fan section in the air-handling system of the presentinvention is substantially uniform whereas the prior art air-handlingsystem has points of higher air velocity and needs time and space to mixso that the flow is uniform by the time it exits the air-handlingcompartment 102, 202. (This can also be described as the higher staticefficiency in that the present invention eliminates the need forsettling means downstream from the discharge of a prior art fan systembecause there is little or no need to transition from high velocity tolow velocity.) The fan array fan section in the air-handling systemtakes in air from the inlet plenum 212 more evenly and efficiently thanthe prior art air-handling system so that the length of the inlet plenum112, 212 may be reduced.

For purposes of comparison, the first exemplary structure set forth inthe Background of the Invention (a structure requiring 50,000 cubic feetper minute of air flow at a pressure of six (6) inches water gage) willbe used. Using the first exemplary structure an exemplary embodiment ofthe present invention could be served by a nominal discharge plenum 210of 89 inches high by 160 inches wide and 30 to 36 inches long (ascompared to 106 to 112 inches long in the prior art embodiments). Thedischarge plenum 210 would include a 3×4 fan array fan section in theair-handling system such as the one shown in FIG. 6) having 12 fan units200. The space required for each exemplary fan unit 200 would be arectangular cube of approximately 24 to 30 inches on a side depending onthe array configuration. The airway path 220 is 42 to 48 inches (ascompared to 88 to 139 inches in the prior art embodiments).

For purposes of comparison, the second exemplary structure set forth inthe Background of the Invention (a structure requiring 26,000 cubic feetper minute of air flow at a pressure of two (2) inches water gage) willbe used. Using the second exemplary structure, an exemplary embodimentof the present invention could be served by a nominal discharge plenum210 of 84 inches high by 84 inches wide, and 30 to 36 inches long (ascompared to 94 to 100 inches long in the prior art embodiments). Thedischarge plenum would include a 3×3 fan array fan section in theair-handling system (such as the one shown in FIG. 7) having 9 fan units200. The space required for each exemplary fan unit 200 would be arectangular cube of approximately 24 to 30 inches on a side depending onthe array configuration. The airway path 220 is 42 to 48 inches (ascompared to 71 to 95 inches in the prior art embodiments).

Reduced Production Costs

It is generally more cost effective to build the fan array fan sectionin the air-handling system of the present invention as compared to thesingle fan unit 100 used in prior art air-handling systems. Part of thiscost savings may be due to the fact that individual fan units 200 of thefan array can be mass-produced. Part of this cost savings may be due tothe fact that it is less expensive to manufacture smaller fan units 200.Whereas the prior art single fan units 100 were generally custom builtfor the particular purpose, the present invention could be implementedon a single type of fan unit 200. In alternative embodiments, theremight be several fan units 200 having different sizes and/or powers(both input and output). The different fan units 200 could be used in asingle air-handling system or each air-handling system would have onlyone type of fan unit 200. Even when the smaller fan units 200 are custommade, the cost of producing multiple fan units 200 for a particularproject is almost always less that the cost of producing a single largeprior art fan unit 100 for the same project. This may be because of thedifficulties of producing the larger components and/or the cost ofobtaining the larger components necessary for the single large prior artfan unit 100. This cost savings also extends to the cost of producing asmaller air-handling compartment 202.

In one preferred embodiment of the invention, the fan units 200 aremodular such that the system is “plug and play.” Such modular units maybe implemented by including structure for interlocking on the exteriorof the fan units 200 themselves. Alternatively, such modular units maybe implemented by using separate structure for interlocking the fanunits 200. In still, another alternative embodiment, such modular unitsmay be implemented by using a grid system into which the fan units 200may be placed.

Reduced Operating Expenses

The fan array fan section in the air-handling system of the presentinvention preferably are less expensive to operate than prior artair-handling systems because of greater flexibility of control and finetuning to the operating requirements of the structure. Also, by usingsmaller higher speed fan units 200 that require less low frequency noisecontrol and less static resistance to flow.

Increased Efficiency

The fan array fan section in the air-handling system of the presentinvention preferably is more efficient than prior art air-handlingsystems because each small fan unit 200 can run at peak efficiency. Thesystem could turn individual fan units 200 on and off to preventinefficient use of particular fan units 200. It should be noted that anarray controller 300 could be used to control the fan units 200. As setforth above, the array controller 300 turns off certain fan units 200and runs the remaining fan units 200 at peak efficiency.

Redundancy

Multiple fan units 200 add to the redundancy of the system, if a singlefan unit 200 breaks down, there will still be cooling. The arraycontroller 300 may take disabled fan units 200 into consideration suchthat there is no noticeable depreciation in cooling or air flow rate.This feature may also be useful during maintenance as the arraycontroller 300 may turn of fan units 200 that are to be maintainedoffline with no noticeable depreciation in cooling or air flow rate.

Sound Attenuation Advantages

The high frequency sound of the small fan units 200 is easier toattenuate than the low frequency sound of the large fan unit. Becausethe fan wall has less low frequency sound energy, shorter less costlysound traps are needed to attenuate the higher frequency sound producedby the plurality of small fan units 200 than the low frequency soundproduced by the single large fan unit 100. The plurality of fan units200 will each operate in a manner such that acoustic waves from eachunit will interact to cancel sound at certain frequencies thus creatinga quieter operating unit than prior art systems.

Reduced Vibration

The multiple fan units 200 of the present invention have smaller wheelswith lower mass and create less force due to residual unbalance thuscausing less vibration than the large fan unit. The overall vibration ofmultiple fan units 200 will transmit less energy to a structure sinceindividual fans will tend to cancel each other due to slight differencesin phase. Each fan unit 200 of the multiple fan units 200 manage asmaller percentage of the total air handling requirement and thusproduce less turbulence in the air stream and substantially lessvibration.

Alternative Embodiments

As mentioned, in one preferred embodiment of the invention, the fanunits 200 are modular such that the system is “plug and play.” Suchmodular units may be implemented by including structure for interlockingon the exterior of the fan units 200 themselves. Alternatively, suchmodular units may be implemented by using separate structure forinterlocking the fan units 200. In still another alternative embodiment,such modular units may be implemented by using a grid system into whichthe fan units 200 may be placed.

FIG. 16 shows an embodiment using an exemplary grid system 230 intowhich the fan units 200 may be placed. In this embodiment the grid maybe positioned and/or built within the air-handling compartment 202. Thefan units 200 may then be positioned into the grid openings, Oneadvantage of this configuration is that individual fan units 200 may beeasily removed, maintained, and/or replaced. This embodiment uses anexemplary unique motor mount 232 that supports the motor 208 withoutinterfering with air flow therearound. As shown, this exemplary motormount 232 has a plurality of arms that mount around the fan inlet cone204. It should be noted that the dimensions of the grid are meant to beexemplary. The grid may be constructed taking into consideration thatthe fan units 200 in the present invention may be spaced with as littleas 20% of a fan wheel diameter between the fan units 200.

FIG. 31 shows an embodiment using either a grid system or modular units240 using separate structure (not shown) for interlocking the fan units200. In this exemplary embodiment, each of the fan units 200 are mountedon a more traditional motor mount 242 within its own fan unit chamber244. In one preferred embodiment, the fan unit 200 and motor mount 242are preferably suspended within their own fan unit chamber 244 such thatthere is an air relief passage 246 therebelow. This air relieve passage246 tends to improve air flow around the fan units 200.

The fan unit chambers 244 shown in FIG. 31 may include one or moreinterior surface made from or lined with an acoustically absorptivematerial or “insulation surface” 248. Going against conventionalindustry wisdom that surfaces cannot be placed in close proximity withthe fan units 200, the present invention places one or more insulationsurfaces 248 at least partially around each fan unit 200 withoutdisrupting air flow. The insulation surfaces 248 may include one or moreof the sides, top, bottom, front, or back. Exemplary types of insulationinclude, but are not limited to traditional insulation board (such asthat made from inorganic glass fibers (fiberglass) alone or with afactory-applied foil-scrim-kraft (FSK) facing or a factory-applied allservice jacket (ASJ)) or alternative insulation such as open cell foamsuch as that disclosed in U.S. patent application Ser. No. 10/606,435,which is assigned to the assignee of the present invention, and whichthe disclosure of which is hereby incorporated by reference herein.Together, the insulation surfaces 248 on the fan unit chambers 244 tendto function as a coplanar silencer. Some of the benefits of using thecoplanar silencer include (1) no added airway length for splitters, (2)no pressure drop, and/or (3) relatively low cost. The acousticadvantages of this and other embodiments make the present inventionideal for use in concert halls, lecture halls, performing arts centers,libraries, hospitals, and other applications that are acousticallysensitive.

FIG. 17 shows airflow between the two panels 20 which representacoustically insulted surfaces and sound attenuation layers. FIGS.17-19A show a first embodiment in which a fiberglass core 22 has an opencell foam 24 layered with at least one side of the fiberglass core 22.FIGS. 17 and 19-22 show a second embodiment combining the use of opencell foam 24 with the use of perforated rigid facing 26. FIG. 22 shows athird embodiment in which the entire insulation board 10 is replacedwith an uncoated open cell foam pad 24.

Turning first to the first embodiment shown in FIGS. 17-19A, thislayered embodiment includes a fiberglass core 22 (or other type ofinsulation) that has an open cell foam 24 layered with at least one sideof the fiberglass core 22. One advantage to using both the fiberglassmaterial and the open cell foam material is that it is less expensivethan using open cell foam material alone because open cell foam moreexpensive than fiberglass. Another advantage to using both thefiberglass material and the open cell foam material is that it weighsless than using fiberglass material alone because fiberglass weighs morethan open cell foam. Another advantage to using both the fiberglassmaterial and the open cell foam material is that is that the twomaterials provide different types of acoustic insulation over adifferent range of frequencies. Together, the two materials providesound absorption over greater range of frequencies. The graph in FIG. 20(shown with a vertical axis as the absorption coefficient going from 0to 1 and a horizontal axis showing the frequency going from 0 to 10,000Htz at approximately the peak point) is meant to be exemplary and doesnot necessarily reflect accurate measurements.

Alternative embodiments of the first layered embodiment include afiberglass core 22 with one side layered with open cell foam 24 (FIG.19A), a fiberglass core 22 with both sides layered with open cell foam24 (FIG. 18), and a fiberglass core 22 and layered with open cell foam24 secured by perforated rigid facing 26 (FIG. 19B). The bottom sectionof FIG. 22 shows the embodiment of FIG. 19A in use in an exemplary airhandler. It should also be noted that an alternative embodiment of thepresent invention could include more than two layers of different typesof insulation. For example, a four layer version could be open cellfoam, fiberglass, rockwool, and open cell foam. The layered embodimentcould actually be “tuned” using different types of insulations,different quantities of insulations, and different thicknesses ofinsulations to have the desired acoustic properties for the intendeduse.

The present invention also includes a method for making an air handlerusing the panels and layers. The method includes the steps of providingan air handler system with at least one air handler surface, providing acore of first insulation material having at least one layering surface,and providing a facing of open cell foam second insulation material.Then, the facing is at least partially layered to the at least onelayering surface to form a layered insulation board. Finally, the atleast one air handler surface is at least partially covered with thelayered insulation board so that the facing is exposed to airflowthrough the air handler.

Turning next to the second embodiment shown in FIGS. 17 and 19-22, thisperf-secured embodiment combines the use of open cell foam 24 with foruse of perforated rigid facing 26. Combining the use of open cell foamand perforated rigid facing 16 provides significant advantages for usein air handlers. For example, the use of the perforated rigid facing 26to secure the open cell foam 24 does not significantly reduce the soundabsorption qualities of the open cell foam 24. As shown in FIG. 19B, theopen cell structure of the open cell foam 24 allows portions of the opencell foam 24 to protrude from openings defined in the perforated rigidfacing 26 (shown in front view in FIG. 21). The exposed open cell foam24 is able to absorb sound waves. In one embodiment, protruding opencell foam 24 formed between the openings in the perforated rigid facing26 absorbs sound waves. This can be compared to prior art embodiments inwhich sound waves are reflected by the substantially rigid diaphragmsformed by the smooth facing 14 being divided by the perforated rigidfacing 16.

Alternative embodiments of the second perf-secured embodiment include afiberglass core 22 and layered with open cell foam 24 secured byperforated rigid facing 26 (FIG. 19) and non-layered open cell foam 24secured by perforated rigid facing 26 (the bottom section of FIG. 22).It should be noted that alternative embodiments may replace perforatedrigid facing 26 shown in FIG. 21 with alternative securing structuresuch as perforated rigid facing 26 with alternatively shaped openings,straps, netting, wire grids, or other securing structure suitable toprevent the open cell foam 24 from being drawn inward.

The present invention also includes a method for making an air handlerusing the perf-secured embodiment. The method includes the steps ofproviding an air handler system with at least one air handler surface,providing open cell foam insulation material, and providing securingstructure through which said facing may be exposed. Then, the at leastone air handler surface is at least partially covered with the open cellfoam insulation material. Finally, the open cell foam insulationmaterial is secured to the at least one air handler surface so that theprotruding open cell foam insulation material is exposed to sound wavesand/or airflow through the air handler.

Turning next to the third preferred embodiment shown in FIGS. 22 and 23,in this uncoated embodiment combines the entire insulation board 10 isreplaced with uncoated open cell foam 24. This would be particularlysuitable for uses in which the presence of fiberglass would not besatisfactory for the intended use or would be unacceptable to theintended client. For example, pharmaceutical companies involved iningestible or injectable drugs would find it unacceptable to have anyfiberglass in the air handler. Alternative embodiments of the seconduncoated embodiment include uncoated open cell foam 24 secured byperforated rigid facing 26 (FIG. 22) uncoated open cell foam 24 securedin a frame 30 (FIG. 23).

The present invention also includes a method for making an air handlerusing the uncoated third embodiment. The method includes the steps ofproviding an air handler system with at least one air handler surfaceand open cell foam. The method also includes the step of covering atleast partially the at least one air handler surface with the open cellfoam.

The present invention is directed to the use of open cell foam in airhandlers that has the necessary durability, safety, and cleanlinessproperties for the particular use. One exemplary open cell foam,melamine foam (Melamine-Formaldehyde-Polycondensate), has been shown tobe quite suitable for this purpose. Melamine is a lightweight, hightemperature resistant, open cell foam that has excellent thermalproperties with superior sound absorption capabilities. Melamine iscleanable in that it is relatively impervious to chemicals (e.g. it isable to withstand relatively caustic cleaning agents such as SPOR-KLENZ®without breaking down). Melamine also meets the flame spread, smokedensity, and fuel contribution requirements necessary to comply withClass-I building code regulations. Because it does not shed particles,it can be used in places where fiberglass would be precluded. Stillfurther, as melamine is inert, it would not cause the health problems(such as those associated with, fiberglass) for those who are exposed tothe product. It also is relatively attractive. It should be noted thatmelamine foam has been used as acoustic insulation by such companies asillbruk (www.illbruk-sonex.com). It should be noted that alternativeopen cell foams could be substituted for melamine. For example, siliconeor polyethane foam could be used as the open cell foam of the presentinvention.

It should be noted that the present invention has been primarilydiscussed in terms of fiberglass as an alternative type of insulation.It should be noted that other types of insulation may be used in placeof fiberglass including, but not limited to rockwool.

Although the embodiments are discussed in terms of layering fiberglassmaterial and the open cell foam material, alternative embodiments couldinclude, bonding the fiberglass material to the open cell foam material,enclosing the fiberglass material within the open cell foam material,coating the fiberglass material with an open cell foam material, andother means for layering the two materials. The term “layers” or“layering” are meant to encompass all of these embodiments as well asothers that would be known to those skilled in the art.

It should be noted that the term “air handlers” is meant to include, byway of example, recirculation air handlers, central air handlers,silencer, splitters (such as parallel splitters), clean room ceilingsystems, and commercial/industrial air handling systems.

FIGS. 24-29 show an exemplary insulated grid system or modular unitsystem interior surfaces are made from acoustically absorptive materialor “insulation surface” 248. In this embodiment, each fan unit cell 244′preferably has a sturdy frame 250 that supports the insulation surfaces248. In one preferred embodiment the frame would form only the edges ofa cube-shaped fan unit cell 244′ and the insulation surfaces 248 wouldform the sides (e.g. top, bottom, and/or sides) of the cube-shaped fanunit cell 244′. In alternative preferred embodiments, the frame mayinclude additional structure or braces for support and/or strength.Together, the insulation surfaces 248 of the fan unit cells 244′ tend tofunction as a coplanar silencer. This is shown graphically in FIGS.25-29 where the coplanar silencer (formed by the insulation surfaces248) reduces the sound wave reaction as the sound waves travel throughthe insulation surfaces 248. For example, in FIG. 25, the central fanunit 200 a is loudest in its own fan unit cell 244′. As the sound of thefan spreads radially, it at least partially dissipates as it passesthrough the surrounding insulation surfaces 248. This is showngraphically as the sound wave circles being darkest in the central fanunit cell 244′ and lighter in the surrounding fan unit cells 244′. Theresult is that the sound from the central fan unit 200 a that eventuallyemanates from the system is softer than sound that would emanate from asystem without the coplanar silencer. In FIG. 26, the first side fanunit 200 b is loudest in its own fan unit cell 244′. As the sound of thefan spreads radially, it at least partially dissipates as it passesthrough the surrounding insulation surfaces 248. This is showngraphically as the sound wave circles being darkest in the central fanunit cell 244′, lighter in the surrounding fan unit cells 244′ and stilllighter in fan unit cells 244′ more distant from the originating fanunit 200 b. The result is that the sound from the fan unit 200 b thateventually emanates from the system is softer than sound, that wouldemanate from a system, without the coplanar silencer. FIG. 27 shows thefirst side fan unit 200 b, a second side fan unit 200 c, and theirrespective sound, waves. As shown graphically in FIG. 30, anotherprinciple of the present invention is that as the sound waves interact,there is a degree of wave cancellation such that the waves areself-extinguishing. FIG. 30 shows wave A and an opposite wave B that areopposites and therefore interact to form a flat wave A+B. If waves arenot exactly opposite, then the combined wave will not be flat, but wouldhave some wave cancellation. This is a basic wave principle of which thepresent invention is able to avail itself. The result of wavecancellation is that the sound from the fan units 200 b and 200 c thateventually emanates from the system is softer than sound that, wouldemanate from, a system without the coplanar silencer. FIG. 28 emphasizesa first corner fan unit 200 d and its wave pattern. FIG. 29 emphasizesboth the first corner fan unit 200 d and a second corner fan unit 200 band their respective wave patterns. The analysis of FIGS. 28 and 29would be similar to that of FIGS. 26 and 27 respectively. It should benoted that in the preferred embodiment, more than two fans might berunning simultaneously and all the running fans would have wavepatterns. The wave patterns of all the running fans would be able totake advantage of both the dissipation (as they pass though surroundinginsulation surfaces 248) and wave cancellation of the coplanar silencer.

In FIG. 31 the discharge plenum 210 (FIG. 3) is positioned within thefan unit chambers 244, and in alternative embodiments the fan unitchambers 244 could enclose the inlet plenum 212, or at least partiallyenclose both the inlet plenum 212 and the discharge plenum 210. Stillother alternative embodiments of fan unit chambers 244 may have grid orwire surfaces (that increase the safety of the present invention) or beopen (that would reduce costs).

Bypass Feature

Multiple fan units enable the array to operate at a range of flow ratesfrom full flow to partial flow where each fan contributes 1/N air flow(where N equals the number of fans). Most direct drive fan systemsoperate at speeds other than full synchronous motor speed in order tomatch the heating or cooling requirements of the structure. Speedcontrol is normally maintained using variable frequency drives. Sincevariable frequency drives are electronic devices, each drive operatingwithin an air handling structure has a certain probability of failure.In a traditional air handling system, if the VFD fails the air handlerwill either shut down or be operated at full synchronous speed of themotor in what is known as bypass mode. In traditional systems fan unitsin the air handler have to be throttled back through some mechanicalmeans in order to limit pressure and flow to meet the buildingrequirements. Mechanical throttling in bypass mode on traditionalsystems creates excessive noise and reduces fan efficiency. The presentinvention overcomes this problem by allowing for a change in the fanarray output by turning certain fans off to meet the design point. Thearray can be tailored to meet the flow and pressure requirement withoutthe need for mechanical throttling and subsequent added noise andreduction in efficiency.

Although FIG. 31 shows the discharge plenum 210 positioned within thefan unit chambers 244, alternative embodiments of fan unit chambers 244could enclose the inlet plenum 212, or at least partially enclose boththe inlet plenum 212 and the discharge plenum 210. Still otheralternative embodiments of fan unit chambers 244 may have grid or wiresurfaces (that increase the safety of the present invention) or be open(that would reduce costs).

FIG. 32 shows an array of dampeners 250 that may be positioned either infront of or behind the fan units 200 to at least partially prevent backdrafts. In the shown exemplary embodiment the dampeners 250 include aplurality of plates, each plate positioned on its own pivot. In theshown exemplary embodiment, the plurality of plates slightly overlapeach other. The shown embodiment is constructed such that when air isflowing through the fan units 200, the plates are in the open positionand when the air stops, gravity pulls the plates into the closedposition. Preferably, each of the dampeners 250 operates independentlysuch that if some of the fan units 200 are ON and some of the fan units200 are OFF, the dampeners 250 can open or close accordingly. Althoughshown as a simple mechanical embodiment, alternative embodiments couldinclude structure that is controlled electronically and/or remotely fromthe dampeners 250.

It should be noted that FIG. 4 shows a 4×6 fan array fan section in theair-handling system having twenty-four fan units 200, FIG. 5 shows a 5×5fan array fan section in the air-handling system having twenty-five fanunits 200, FIG. 6 shows a 3×4 fan array fan section in the air-handlingsystem having twelve fan units 200, FIG. 7 shows a 3×3 fan array fansection in the air-handling system having nine fan units 200, and FIG. 8shows a 3×1 fan array fan section in the air-handling system havingthree fan units 200. It should be noted that the array may be of anysize or dimension of more than two fan units 200. It should be notedthat although the fan units 200 may be arranged in a single plane (asshown in FIG. 3), an alternative array configuration could contain aplurality of fan units 200 that are arranged in a staggeredconfiguration (as shown in FIG. 15) in multiple planes. It should benoted that cooling coils (not shown) could be added to the system eitherupstream or downstream of the fan units 200. It should be noted that,although shown upstream from the fan units 200, the filter bank 122, 222could be downstream.

It should be noted that an alternative embodiment would use ahorizontally arranged fan array. In other words, the embodiments shownin FIGS. 3-15 could be used horizontally or vertically or in anydirection perpendicular to the direction of air flow. For example, if avertical portion of air duct is functioning as the air-handlingcompartment 202, the fan array may be arranged horizontally. Thisembodiment would be particularly practical in an air handlingcompartment for a return air shall.

It should be noted that the fan section 214 may be any portion of theairway path 220 in which the fan units 200 are positioned. For example,the fan units 200 may be situated in the discharge plenum 210 (asshown), the inlet plenum 212, or partially within the inlet plenum 212and partially within the discharge plenum 210. It should also be notedthat the air-handling compartment 202 may be a section of air duct.

Control System

Turning now to FIG. 33, an electronic controller 300 may be implementedto automatically select a number of operative fan units and the RPMspeed of each fan unit in order to achieve a predetermined or desiredlevel of efficiency for the overall fan array. For example, the desiredlevel of efficiency may be to approximately maximize the efficiencies,to attain a high percentage efficiency (e.g., 90%, 80%, etc.) and thelike. In certain applications, fan units may achieve the desired levelof efficiency within a narrow RPM range. In an exemplary embodiment, thecontroller 300 operates in a feedback control loop to maintain the fanunits 200 continuously operating in a desired efficiency range. Thecontroller 300 varies the airflow and/or static pressure continuously orperiodically by varying the number of fan units 200 operative within thearray as environmental parameters for the building change. By way ofexample, environmental parameters for a building include airflow,humidity, temperature and the like. For example, a target environmentalparameter for airflow may be set to one-half of a maximum fan-arrayairflow capacity during the day and 40% at night. Thus the controller300 may only turn on half of the fan units 200 within the fan-arrayduring the day and turn on 40% of the fan units at night. In this way,energy consumption may be greatly reduced.

The controller 300 achieves a desired level of efficiency of the fanarray through the use of an iterative process as shown in FIG. 33.Building management provides environmental parameters or programmedconstraints, at 304, based on the air handling needs at a given time orover repeated time intervals. These environmental parameters orconstraints 304 may include factors such as static pressure, totalairflow, humidity, temperature and the like for desired time periods(e.g., day, night, week days, weekend, etc.). Initially, the controller300 sets an initial number of operative fans to a predetermined number(e.g. one) and sets an initial RPM speed to a predetermined level (e.g.,a fan minimum or a percentage of the motor maximum rated RPM speed,etc.). At 306, the controller 300 calculates a static pressure based onthe current number of operative fans and the current RPM speed for apredetermined CFM. Next, at 308, the controller 300 determines whetherthe candidate static pressure satisfies (e.g. corresponds to) theprogrammed constraints (e.g., programmed static pressure environmentalparameter) that was input by the building management operator. If not,flow moves to 310, where it is determined whether the current RPM speedhas reached a maximum for the motor or fan. If not, flow moves to 312where the RPM speed is incremented by a predetermined amount and a newcandidate static pressure is recalculated at 306.

If at 310, the RPM speed has reached the maximum rated level of themotor or fan, then flow moves to 318 where the number of operative fansis incremented by a predetermined amount. At 318, the RPM speed is resetto the initial RPM speed. Next, a new candidate static pressure iscalculated at 306. The controller 300 repeats the calculations at306-318 until the candidate static pressure corresponds to the staticpressure input by the building management operator, which represents theRPM speed at which a number of the fan units 200 should be run in orderto satisfy the programmed environmental parameters or constraints. Forexample, the number of fans may represent a single fan unit 200, two fanunits 200, and all numbers of fan units 200 up to the total number offan units 200 in the system. At 314, the controller 300 records, inmemory, the RPM speed and number of operative fan units as a potentialor candidate RPM/fan unit combination that would achieve theprogrammed/input static pressure.

Next at 316, the controller 300 determines whether the candidate numberof operative fan units equals the total number of fan units in the fanarray. If not, flow returns to 318 where the number of operative fanunits is again incremented and the RPM speed is reset to the initial RPMspeed. If the candidate number of operative fan units equals the totalnumber of fan units in the fan array, flow moves to 320. As the processiterates through the operation at 314, a table of potential RPM/fan unitcombinations is created where each entry in the table includes acombination of a candidate RPM speed and a number of operative fan unitsfor the associated input static pressure. Optionally, the candidate RPMspeed and number of operative fan units may be saved as the solecandidate for the corresponding static pressure and the remainingoperations 316-324 of FIG. 19 omitted. Once the calculation 306-318 iscompleted, the controller 300 has created and saved multiplecombinations of candidate RPM speeds and candidate number of operativefan units that each achieves the programmed or input static pressure.

Continuing in FIG. 33, at 320, the controller 300 successively analyzeseach of the potential RPM/fan unit combinations saved in the tablecreated at 314. For each entry in the table, the controller 300calculates the horsepower required to run the corresponding number ofoperative fan units 200 (e.g., for each combination of candidate RPMspeeds and candidate number of operative fan units that achieve theprogrammed static pressure).

For example, if one of the potential RPM/fan unit combinations in thetable indicated that 5 fan units were to be operative at 2000 rpms, thecontroller 300 would calculate the power usage of each of the five fanunits for the corresponding 2000 rpm speed. Similarly, if anotherpotential RPM/fan unit combination in the table indicated that 10 fanunits should be operative at 1500 rpms, the controller would calculatethe power usage of each of the 10 fan units at 1500 rpms. Once the powerusage is calculated for each potential RPM/fan unit combination, thecontroller 300 then identifies at 322 a resultant RPM/fan unitcombination that utilizes the desired power usage (e.g., lowest power).From the table of potential RPM/fan, unit combinations, the system mayselect, at 322, the resultant RPM/fan unit combination that requires theleast horsepower. Then at 324, the controller 300 turns fan units 200 onor off until the number of operative fan units 200 corresponds to theresultant RPM/fan unit combination. At 324, the controller 300 adjuststhe speed of the fan units 200 that are operative to correspond to theRPM speed indicated in the resultant RPM/fan unit combination. In thisway, the system will continuously select an efficient combination of thenumber of operative fan units 200 and fan unit RPM speed to satisfy theprogrammed constraints 304 provided by the building management operator.

The fan array may be run by a single Variable Frequency Drive (VFD)device. Optionally, a second VFD may be available for redundancypurposes. The speed at which the fan units 200 run may be the same forall fans which corresponds to the result and RPM speed. Optionally, setsor groups of the fan units 200 may be coupled to different VFD devices,such that the RPM speed of each set or group of fan units 200 may beindependently controlled. For example, separate VFDs may be coupled toeach row, or each column, of fan units 200. The fan units in each row orcolumn may then be set to a common RPM speeds (e.g., 1^(st) and lastrows set to operate at 2000 rpms, while middle rows are set to operateat 3000 rpms). Optionally, the each fan unit 200 may be coupled to (orintegrated with) a corresponding unique VFD device, such that the RPMspeed of each fan unit 200 may be independently controlled.

As a further option, multiple VFDs may be made generally availablewithout a direct relation to any particular motor. The VFDs may beconfigured to be dynamically coupled to one or more corresponding fanunits 200 at run time. In this example, the number of VFDs may be usedthat correspond to the number of different RPM speeds that are, to beutilized simultaneously. For example, one of the multiple VFD may becoupled to a first set of fan units 200 that are set at an RPM speed of2000 rpm, while a second of the multiple VFD may be coupled to a secondset of fan units 200 that are set at an RPM speed of 3000 rpm.

The calculations at 306 may be made based upon fan curves 302 providedby the manufacturer at the time of installation. Fan curves 302 arecalculated by taking an individual fan unit 200 and measuring its staticpressure output and horsepower input as a function of total airflow.This measurement may occur inside of the air-handling system installedin the building, because the results will vary based on, for instance,the size, shape, and configuration of the plenum in which the fan units200 are placed. The resulting data may then be fitted with a polynomialcurve—the fan curve 302—preferably of fifth or sixth order, with theindependent variable being the airflow. The coefficients for each powerof the independent variable corresponding to the best-fit curve arefound and recorded. Commercially available data analysis software issuitable for this task. When the fitting process is complete, anequation is obtained that will accurately give the static pressure of asingle fan unit 200 at a particular airflow. The total static pressureof the system is then given by a summation equation as follows:

${\sum\limits_{n = 0}^{X}\;{C_{n}{{CFM}^{n}\left( \frac{Df}{Ef} \right)}^{n}\left( \frac{Ds}{Es} \right)^{n - 2}}},$where Cn is the nth power coefficient from the static pressurepolynomial curve fit described above, CFM is the airflow in cubic feetper minute, Df is the total number of fan units 200 in the system, Ef isnumber of operative fan units 200, Ds is the design maximum speed of thefan units 200, Es is the actual operating speed of the fans, and X is athe order of the polynomial used for the static pressure curve fit.Given a static pressure and a required airflow, the controller 300 mayiteratively determine at 306-318 the RPM speed of the fan units 200 foreach number of operative fan units 200 by inserting different values ofRPMs, at 312, into the static pressure equation calculated at 306 untilthe desired static pressure is reached at 308. This process is repeated318 for a single fan unit 200, two fan units 200, and so on until thetotal number of fan units 200 in the array has been reached. Each of theRPM values is then recorded 314 for use by the horsepower calculation320. The use of a computer greatly speeds the process of finding thenecessary fan unit speed for each of the various numbers of operativefan units 200.

As described above, a polynomial curve, again preferably of fifth orsixth order, is also fitted to the data showing brake horsepower as afunction of airflow for an individual fan unit 200, and the totalconsumption of the array is then be calculated by summing theconsumption of individual fan units 200. The result of the speedcalculation given above is used to simplify the horsepower calculation.After calculating the necessary fan unit speed for each number ofoperative fans, the resultant operative number/RPM pairs is passed tothe brake horsepower equation given by

${\sum\limits_{n = 0}^{X}\;{C_{n}{{CFM}^{n}\left( \frac{Df}{Ef} \right)}^{n - 1}\left( \frac{Ds}{Es} \right)^{n - 3}}},$where Cn is the nth power coefficient of the horsepower polynomial curvefit described above, CFM is the airflow in cubic feet per minute, Df isthe total number of fan units 200 in the system, Ef is number ofoperative fan units 200, Ds is the design maximum speed of the fan units200, Es is the operating speed of the fans taken from the staticpressure equation, and X is a the order of the polynomial used for thehorsepower curve fit. The controller 300 may then calculate 320 thepower consumption of the one fan case, the two fan case, and so on up tothe total number of fan units 200 based upon the RPM information 314from the static pressure equation 306. It is then a simple matter forthe controller 300 to identify 322 a preferred number of fan units 200and the fan unit speed that will achieve a desired level of powerconsumption. The controller 300 may then optionally directly adjust 324the number of operative fan units 200 to achieve the desired level ofpower consumption, or it may optionally output a suggestion for a humanoperator to implement manually. In an exemplary embodiment, thecontroller 300 recalculates the optimal number of operative fan units200 at an interval of less than one minute. The frequency ofrecalculation is limited only by the speed of the computer performingthe calculation. In this way, changes in the building's needs may berapidly implemented and high efficiency achieved at all times.

The controller 300 may be implemented in any of a number of ways. Forinstance, a general purpose computer may be programmed to control thefan array. Alternatively, a programmable logic controller, in anexemplary embodiment, the Siemens S7 controller, may be programmed withthe necessary algorithm. Either of these may use variable-frequencydrives, controlled by a digital signal, to control fan unit speed, anddigitally-controlled relays to switch fan units 200 on and off. In thealternative, the actual control of fan units 200 may be accomplished bymanual switches and rheostats manipulated by human operators. Thecontroller 300 may include a stand alone computer, laptop computer, aprogrammable microcontroller or processor which performs the variousoperations discussed herein. The controller 300 may include amicroprocessor, or equivalent control circuitry and may further includeRAM or ROM memory, logic and timing circuitry, state machine circuitry,and I/O circuitry. The details of the design and operation of thecontroller 300 are not critical to the present invention. Rather, anysuitable controller 300 may be used that carries out the functionsdescribed herein.

FIG. 34 illustrates a process for calculating motor load-efficiency thatmay be carried out in connection with an alternative embodiment. Forexample, the process of FIG. 34 may be inserted into the process of FIG.33 in place of the horsepower calculation operation at 320. The electricmotors coupled to the fan units are generally configured to operate at40% to 100% of the rated load (e.g., the rated horsepower). For example,a motor with a rated load of 10 horsepower (hp) may be configured tooperate between 4 and 10 hp. Each motor exhibits a varying amount ofefficiency depending, in part, on where the motor operates relative tothe motor rated load. For example, a motor may exhibit peak efficiencywhen operated at or near 70% or 85% of the motor rated load. As afurther example, a motor having a 10 hp rated load may have anacceptable load range of 4 to 10 hp, with a peak efficiency at 7.5 to8.5 hp. Motor efficiency may decrease as the motor's operating loadmoves below 40% of the rated load or moves near 100% of the rated load.The efficiency curve for motors varies between individual motors andbased on motor size and rated load.

The process of FIG. 34 analyzes values for various motor controlparameters to determine which values will result in the motor operatingwith a desired level of motor efficiency. At 402, the table of candidateRPM/fan unit combinations (that was created at 314 in FIG. 33) isaccessed and the first candidate combination is analyzed. At 404, a testmotor RPM speed is set to correspond to the candidate RPM speed in thefirst candidate combination from the table. At 406, the controller 300calculates the current motor load (e.g., in working horsepower) thatwould be experienced for an individual fan unit when operated at thetest motor RPM speed. The current motor load is then compared to themotor's full load (e.g., maximum horsepower) to obtain a percentage fullmotor load that would be drawn by the motor when operating at the testmotor candidate RPM speed. For example, if the test motor candidate RPMspeed were 3000 rpm, the controller 300 may determine that this motorwill operate at 7 horsepower. If the motor has a full or maximum load of10 hp, then 7 hp would be a 70% of the full motor load.

Next, at 408 the controller 300 determines the motor efficiency from thepercentage full motor load calculated at 406. The motor efficiency maybe determined through algorithmic analysis, or from efficiency tables,or from a motor load-efficiency curve, or a combination thereof and thelike. For example, if a motor is operating at 70% of full motor load, aload-efficiency curve may indicate that this motor has an efficiency of90% when at 70% full motor load. Once the motor efficiency has beendetermined, then at 410 the controller 300 records the motor efficiency,the corresponding RPM speed, the percentage load and the number ofoperative fan units in a table as a motor-refined candidate RPM/fan unitcombination. The foregoing information may be recorded in the same tableor a different table as utilized at 314 to record the candidate RPM/fanunit combinations.

Next at 412, the controller 412 determines whether the test motor RPMspeed is the last or only available RPM speed for the current number offan units. If not, flow moves to 416 where the RPM speed is set to a newRPM speed. For example, the RPM speed may be increased or decreased by aset amount at 416. Next, the operations at 406 to 410 are repeated and anew motor-refined candidate RPM/fan unit combination is obtained andsaved in the table. The operations at 406 to 410 are repeated until thecurrent number of operative fan units has no more available RPM speedsthat may be used. For example, the RPM speed may be successively steppedthrough a range of RPM speeds that start at a set number of RPMs or at aset percentage below the candidate RPM speed. The operation at step 418may up the RPS speed until reaching an RPM speed that is a set number ofRPMs, or a set percentage, above the candidate RPM speed. Once theavailable RPM speeds are analyzed for the current number of operativefan units, flow moves from 412 to 414.

At 414, the controller determines whether additional candidate RPM/fanunit combinations exist in the table created at 314 (FIG. 33). Forexample, if the table includes ten candidate RPM/fan unit combinations,and there are five available RPM speeds that are desired to be testedwith each combination, then the operations at 406 to 412 are repeatedfive times (one for each of the 5 available RPM speeds) for each of theten candidate RPM/fan unit combinations. In the foregoing example, theoperations at 406 to 414 would create a table with 50 motor-refinedcandidate RPM/fan unit combinations. Thereafter, flow returns to 322 inFIG. 33. Returning to FIG. 33, at 322, the controller 300 selects themotor-refined candidate RPM/fan unit combination that exhibited adesired motor efficiency and static pressure.

FIG. 35 illustrates a multi-tier speed array processing sequence carriedout in accordance with an alternative embodiment to calculate multiplesets of operative fan units where each set of operative fan unitsincludes a different RPM speed. Beginning at 502, the number of tiers isset. For example, two or three different RPM speeds may be programmed tobe used at the same time. For example, interior fan units may beoperated at a higher RPM speed, while peripheral fan units may beoperated at a lower fan speed, or vice versa. Alternatively, operativefan units in each row or each column may be alternately assigned firstand second RPM speeds. Thus, adjacent fan units may have different RPMspeeds, while all of the operative fan units assigned the first RPMspeed are interleaved with the operative fan units assigned the secondRPM speed. For example, a fan array may be divided into four quadrants,with each quadrant assigned a different RPM speed. As a further example,operative fan units in a first quadrant of the fan array may be assigneda common RPM speed, while one or more quadrants of the fan array may beassigned a different RPM speed. Alternatively, opposed quadrants may beassigned a common RPM speed.

Returning to FIG. 35, at 503 the controller 300 calculates the portionof the total static pressure to be contributed by each of the tiers. Thetier contributions may be equal or different. The tier contributions maybe proportional to the number of fan units in each tier. For example, ifa first tier includes 50% of the total fan units, a second tier includes25%, a third tier includes 15% and a fourth tier includes 10%, then eachtier would be assigned a corresponding percentage (50%, 25%, 15%, 10%)of the programmed static pressure.

Next, at 504, the controller calculates the number of operative fanunits and the RPM speed for a current tier. For example, in a two tier25 fan unit array, where the first and second tiers include 75% and 25%,respectively, of the total fan units, then 75% and 25% of the staticpressure would be attributed to each tier. Hence, tier one may utilize10 operative fan units out of 15 total fan units, while tier two mayutilize 2 operative fan units out of 5 total fan units.

Next at 506 the RPM speed and number of operative fan units for acurrent tier may be refined based on motor efficiencies as discussedabove in connection with FIG. 34. Optionally, the operation at 506 maybe omitted entirely. Next at 508 it is determined whether all of thetiers have been analyzed and assigned RPM speeds and numbers ofoperative fan units. If not, flow moves to 510 where the current tier isincremented. The operations at 504 and 506 are repeated for the nexttier. When at 508 it is determined that no more tiers exist, the processis completed.

FIG. 36 illustrates a fan array reconfiguration process implemented inaccordance with an alternative embodiment. At 602, the controller 300determines a current or initial configuration of operative fan units.For example, the initial configuration of operative fan units mayresemble a checker pattern where alternate fan units are ON andalternate fan units are OFF. After 602, alternative steps may beimplemented. For example, in accordance with one embodiment, flow maymove to 604 where the controller 300 accesses a collection of storedtemplates or stored preprogrammed patterns of operative fan units.Optionally, at 606, the controller 300 may implement an algorithm toautomatically calculate a new pattern for the operative fan units. Next,at 608, the controller 300 may update the current pattern of operative,fan units with a new pattern of operative fan units from the templatesor preprogrammed patterns at 604, or calculated at 606.

Different patterns may be preprogrammed or automatically calculated toevenly distribute the life cycle of the fan units. For example, if afirst pattern resembles a checker pattern, the second pattern mayinclude the gaps in the first pattern. Thus, if the first pattern ofoperative fan units includes fan units #1, #3, #5, and #7 in the firstrow, the second pattern of operative fan units may include the fan units#2, #4, #6 and #8. The controller 300 may periodically (e.g., everymonth, every quarter, etc) switch from one pattern to a differentpattern. For example, it may be desirable to switch patterns to evenlydistribute the life cycle between the fan units. Hence, over amulti-year period, all or most of the fan units would experiencesubstantially equal amounts of operation time.

As a further option, the pattern of operative fan units may only beswitched for shorter “cycle” periods of time. For example, once eachweek, each month, each quarter, etc., the fan units that are normallyOFF may be “cycled” by turning them ON, while at least a portion of thefan units that were otherwise ON are turned OFF. The fan units that aretemporarily cycled ON may remain ON only for a short period of time(e.g., an hour, a day, etc.). Cycling fan units ON for short periods oftime may be desirable to avoid damage, to the bearings and other partsof the motor and fan, that may result from remaining stationary forexcessively long periods of time (e.g., to avoid flat spots forming onbearings).

FIG. 37 illustrates a local fan array control system 640 that may beimplemented in connection with an embodiment of the present invention.The control system 640 is “local” in that it is physically located inrelatively close proximity to the fan array. For example, the controlsystem 640 may be integrated into a common framework with the fan array.Alternatively, the control system 640 may be located within the samebuilding or within a common building campus/complex as one or more fanarrays that are controlled by the control system 640. The control system640 includes a controller 650 that performs the functions discussedabove in connection with FIGS. 33-36. The controller 650 may resemblethe controller 300. The controller 650 is electrically coupled to anarray of motors 652-655 which represent the motors within, and thatdrive, the fan units 200. It should be realized that more or fewermotors and switches may be utilized as indicated by the dashed linearrows.

The controller 650 is also electrically connected, over acommunications/switch line 686, to one or more variable frequency drives(VFD) 672 and 674. The VFD 674 may be a redundant VFD that is onlyactivated when the primary VFD 672 fails or is serviced. Thecommunications/switch line 686 enables the controller 650 to controloperation of the VFDs 672, 674. The communications/switch line 686 alsocontrols the state (e.g., open or closed) for switches 682 and 684. Byopening or closing the switches 682 and 684, the controller 650 connectsone or both of the VFDs 672 and 674 to the motors 652-655. The VFD 672provides a pulse width modulated (PWM) power signal to the motors652-655, where the pulse width is changed to control the RPM speed ofthe motors 652-655.

The controller 650 is connected over a motor switch line 668 to a seriesof switches 662-665 which correspond in a one to one relation with themotors 652-655. The controller 650 controls the open or closed state ofthe switches 662-665 to render a select combination of the motors652-655 operative. The number and combination of motors 652-655 that arerendered operative corresponds to the number of operative fan unitscalculated above in connection with FIGS. 33-36. The motors 652-655 areconnected to a feedback line 670 through which the controller 650obtains information regarding the motor operational status. Optionally,the feedback line 670 may be connected to sensors that provide measuredvalues such as for the flow rate (in cubic feet per minute), the statuspressure, and the like.

Optionally, it may be desirable to use multiple VFDs 672 and 674 at thesame time to control different portions of the fan units. By way ofexample, the first VFD 672 may be connected only to half of the motors652 and 653, while the second VFD 674 is connected to a remaining halfof the motors 654 and 655.

The controller 650 may be implemented as a remote computer, a laptop andthe like. The lines 686, 668 and 670 may be serial lines, parallelbuses, internet lines and the like. Optionally, the lines 686, 668 and670 may be replaced with wireless links wherein the controller 650communicates wireless with one or more of the VFDs 672, 674, switches682,684, switches 662-665, motors 652-655, and sensors (e.g, over a WiFilink, LAN, WAN, etc.). For example, the system controller 650 may bepart of the building management system (BMS) that includes aworkstation, operator user interface, display, etc. The BSM may beconfigured to implement the functionality of the controller that isdescribed above.

FIG. 38 illustrates a distributed fan array control system 700 inaccordance with one embodiment. The distributed fan array control system700 includes a server 702 that is connected to a database 704, ahardwired fan array interface 706, a wireless fan array interface 708and a user workstation 710 electrically connected to a communicationsystem 712. The system 700 may be used to support remote control,configuration and monitoring of fan arrays 720, 722. For example, thework station 710 or server 702 may perform the above discussedcalculations as to the RPM speed and number of operative fan units. Theresultant RPM/fan unit combination may be passed over the internet, atelephone line or a dedicated local or wide area network to the fanarray 720, 722, such as through wireless or hardwired fan arrayinterfaces 708 and 706. Optionally, a fan array may transmit messagesthrough the wireless or hardwired fan array interfaces 708 and 706 to asystem operator such as at user workstation 710, PDA 718, cell phone716, etc. The fan array 720, 722 may transmit notices and feedback to anoperator regarding errors that occur a predetermined number of times orfor a predetermined amount of time in one day or one week. The server702 may keep records to determine where to route a service notice. Theserver 702 may retain the BSM inputs requesting particular environmentalparameters or programmed constraints, the tables of candidate andresultant RPM/fan unit combinations, the motor load-efficiency curves,the fan curves, etc. The server may perform the calculations discussedabove in connection with FIGS. 33-36.

The communication system 712 may be the internet, a voice over IP (VoIP)gateway, a local plain old telephone service (POTS) such as a publicswitched telephone network (PSTN), and the like. Alternatively, thecommunication system 712 may be a local area network (LAN), a campusarea network (CAN), a metropolitan area network (MAN), or a wide areanetwork (WAM). The server 702 interfaces with the communication system712, such as the internet or a local POTS based telephone system, totransfer information between the programmer 706, the wireless fan arrayinterface 708, the user workstation 710 as well as a cell phone 716, anda personal data assistant (PDA) 718 to the database 704 forstorage/retrieval of records of information. For instance, the server702 may download, via a wireless connection 726, to the cell phone 716or the PDA 718 the results of resultant RPM/fan unit combinations. Onthe other hand, the server 702 may upload raw fan array data from fanarrays 720 and 722.

Database 704 is any commercially available database that storesinformation in a record format in electronic memory. The database 704stores information such as fan curves, past operation time,load-efficiency curves/tables, candidate and resultant RPM/fan unitcombinations, motor parameters, and the like. The information isdownloaded into the database 704 via the server 702 or, alternatively,the information is uploaded to the server from the database 704.

The interfaces 706 and 708 interface with the fan arrays 720 and 722.The wireless communicate may utilize protocols, such as Bluetooth, GSM,infrared wireless LANs, HIPERLAN, 3G, satellite, as well as circuit andpacket data protocols, and the like. The user workstation 710 mayinterface with the communication system 712 via the internet or POTS todownload information via the server 702 from the database 704.

FIG. 39 illustrates a block diagram of example manners in whichembodiments of the present invention may be stored, distributed, andinstalled on a computer-readable medium. In FIG. 39, the “application”represents one or more of the methods and process operations discussedabove. The application is initially generated and stored as source code800 on a source computer-readable medium 802. The source code 800 isthen conveyed over path 804 and processed by a compiler 806 to produceobject code 808. The object code 808 is conveyed over path 810 and savedas one or more application masters on a master computer-readable medium812. The object code 808 is then copied numerous times, as denoted bypath 814, to produce production application copies 816 that are saved onseparate production computer-readable media 818. The productioncomputer-readable media 818 are then conveyed, as denoted by path 820,to various systems, devices, terminals and the like.

A user terminal 822, a device 824 and a system 826 are shown as examplesof hardware components, on which the production computer-readable medium818 are installed as applications. (as denoted by 828 through 832). Forexample, the production computer-readable medium 818 may be installed onthe controller 300. Examples of the source, master, and productioncomputer-readable medium 802, 812, and 818 include, but are not limitedto, CDROM, RAM, ROM, Flash memory, RAID drives, memory on a computersystem, and the like. Examples of the paths 804, 810, 814, and 820include, but are not limited to network paths, the internet, Bluetooth,GSM, infrared wireless LANs, HIPERLAN, 3G, satellite, and the like. Thepaths 804, 810, 814, and 820 may also represent public or privatecarrier services that transport one or more physical copies of thesource, master, or production computer-readable media 802, 812 or 818between two geographic locations. The paths 804, 810, 814 and 820 mayrepresent threads carried out by one or more processors in parallel. Forexample, one computer may hold the source code 800, compiler 806 andobject code 808. Multiple computers may operate in parallel to producethe production application copies 816. The paths 804, 810, 814, and 820may be intra-state, inter-state, intra-country, inter-country,intra-continental, inter-continental, and the like.

The operations noted in FIG. 39 may be performed in a widely distributedmanner world-wide with only a portion thereof being performed in theUnited States. For example, the application source code 800 may bewritten in the United States and saved on a source computer-readablemedium 802 in the United States, but transported to another country(corresponding, to path 804) before compiling, copying and installation.Alternatively, the application source code 800 may be written in oroutside of the United States, compiled at a compiler 806 located in theUnited States and saved on a master computer-readable medium 812 in theUnited States, but the object code 808 transported to another country(corresponding to path 814) before copying and installation.Alternatively, the application source code 800 and object code 808 maybe produced in or outside of the United. States, but productionapplication copies 816 produced in or conveyed to the United States (forexample, as part of a staging operation) before the productionapplication copies 816 are installed on user terminals 822, devices 824,and/or systems 826 located in or outside the United States asapplications 828 through 832.

As used throughout the specification and claims, the phrases“computer-readable medium” and “instructions configured to” shall referto any one or all of (i) the source computer-readable medium 802 andsource code 800, (ii) the master computer-readable medium and objectcode 808, (iii) the production computer-readable medium 818 andproduction application copies 816 and/or (iv) the applications 828through 832 saved in memory in the terminal 822, device 824, and system826.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventionwithout departing from its scope. While the dimensions and types ofmaterials described herein are intended to define the parameters of theinvention, they are by no means limiting and are exemplary embodiments.Many other embodiments will be apparent to those of skill in the artupon reviewing the above description. The scope of the invention should,therefore, be determined with reference to the appended claims, alongwith the full scope of equivalents to which such claims are entitled. Inthe appended claims, the terms “including” and “in which” are used asthe plain-English equivalents of the respective terms “comprising” and“wherein.” Moreover, in the following claims, the terms “first,”“second,” and “third,” etc. are used merely as labels, and are notintended to impose numerical requirements on their objects. Further, thelimitations of the following claims are not written inmeans-plus-function format and are not intended to be interpreted basedon 35 U.S.C. §112, sixth paragraph, unless and until such claimlimitations expressly use the phrase “means for” followed by a statementof function void of further structure.

The terms and expressions that have been employed in the foregoingspecification are used as terms of description and not of limitation,and are not intended to exclude equivalents of the features shown anddescribed or portions of them. The scope of the invention is defined andlimited only by the claims that follow.

What is claimed is:
 1. A control system for an air handling systemhaving a preselected number of fan units, said fan units arranged in afan array, said array capable of operation with a number of operativefan units less than the preselected number of fan units, the controlsystem comprising: a controller calculating multiple combinations ofcandidate fan unit speeds and numbers of operative fan units configuredto provide at least one of a common select static pressure or commonselect airflow; wherein, after calculating the multiple combinations,the controller automatically selects one of the combinations ofcandidate fan unit speeds and number of operative fan units so as topermit the operative fan units to run at a desired level while providingthe at least one of a common select static pressure or common selectairflow.
 2. The air handling system of claim 1 wherein the controllercalculates the combinations by calculating a necessary fan unit speed togive a selected static pressure at a selected airflow for candidatenumbers of operative fan units.
 3. The air handling system of claim 2wherein a calculated static pressure at the selected airflow is given bythe equation${\sum\limits_{n = 0}^{X}\;{C_{n}{{CFM}^{n}\left( \frac{Df}{Ef} \right)}^{n}\left( \frac{Ds}{Es} \right)^{n - 2}}},$where C_(n) are coefficients determined by system design, CFM is theselected airflow in cubic feet per minute, Df is the preselected numberof fan units in the system, Ef is the number of operative fan units,which is iteratively incremented, Ds is a design maximum speed of thefan units, Es is a speed of the fan units, which is iterativelyincremented, and X is the total number of coefficients.
 4. The airhandling system of claim 3 wherein the values of coefficients C_(n) arecalculated by a method comprising the steps of: a. measuring anempirical static pressure as a function of an empirical airflow for asingle fan unit; b. fitting the resulting data with a polynomial oforder m, where m is an integer; c. setting the value of C_(n) equal tothe coefficient of the nth-power term of the fitted polynomial for nrunning from zero to m; and d. setting X equal to m.
 5. The air handlingsystem of claim 1 wherein the controller calculates the combinations byiteratively incrementing fan unit speed and the number of operative fanunits.
 6. The air handling system of claim 1 wherein the controllercalculates the combinations through an interactive feedback controlloop.
 7. The air handling system of claim 1 wherein the controllercalculates the combinations by calculating a power level required tooperate the fan array at a selected static pressure, a selected airflow,and with different numbers of operative fan units, and then adjustingthe number of operative fan units and a speed of the fan units toachieve a select power level.
 8. The air handling system of claim 7wherein the controller calculates the power level required using theequation${\sum\limits_{n = 0}^{X}\;{C_{n}{{CFM}^{n}\left( \frac{Df}{Ef} \right)}^{n - 1}\left( \frac{Ds}{Es} \right)^{n - 3}}},$where C_(n) are coefficients determined by system design, CFM is theselected airflow in cubic feet per minute, Df is the preselected numberof fan units in the system, Ef is number of operative fan units, whichis iteratively incremented, Ds is a design maximum speed of the fanunits, Es is a speed of the fan units, which is iteratively incremented,and X is the total number of coefficients.
 9. The air handling system ofclaim 8 wherein the values of coefficients C_(n) are calculated by amethod comprising the steps of: a. measuring the power level as afunction of airflow for a single fan unit; b. fitting the resulting datawith a polynomial of order m, where m is an integer; c. setting thevalue of C_(n) equal to the coefficient of the nth-power term of thefitted polynomial for n running from zero to m; and d. setting X equalto m.
 10. The air handling system of claim 1, wherein the controllercalculates combinations of candidate fan unit speeds and numbers ofoperative fan units that satisfy programmed environmental parameters.11. The air handling system of claim 1, wherein the controller selectsone of the combinations to permit the operative fan units to operate ina desired efficiency range.
 12. The air handling system of claim 1,wherein the controller is configured to adjust a set of parameters ofthe fan units based on at least one of fan unit power usage and motorload.
 13. The air handling system of claim 1, wherein the controller isconfigured to: a. calculate a power usage for a plurality of candidateRPM and fan unit combinations; b. select one of the candidate RPM andfan unit combinations based on a corresponding power usage; and c.adjust operating parameters of the fan units to correspond to theselected one of the candidate RPM and fan unit combinations.
 14. The airhandling system of claim 1, wherein the controller is configured vary atleast one of air flow volume and static pressure, in a feedback controlloop as environmental parameters for a building change.
 15. The airhandling system of claim 1, wherein the controller achieves a desiredlevel of efficiency of the fan array through an iterative process ofcalculating the combinations and selecting one of the combinations. 16.The air handling system of claim 1, wherein the controller performs theautomatic selection based on programmed environment parameters thatinclude at least one of airflow volume, static pressure, humidity andtemperature.
 17. The air handling system of claim 1, wherein, for eachcombination, the controller calculates multiple sets of operative fanunits where each set of operative fan units has a different associatedfan unit speed, the controller selecting one combination such that firstand second sets of operative fan units operate at the same time but withdifferent corresponding first and second fan unit speeds.
 18. The airhandling system of claim 1, wherein the controller automaticallycalculates a pattern for the operative fan units.
 19. The air handlingsystem of claim 1, wherein the controller selects a pattern frompreprogrammed patterns or automatically calculates the pattern.
 20. Thecontrol system of claim 1, further comprising: a. a user input, for thecontroller, configured to permit a user to program the desired level;and b. an output from the controller configured to be coupled to the fanarray.
 21. The control system of claim 1, further comprising a fan arrayof a preselected number of fan units.
 22. The control system of claim 1,wherein the controller is configured to take the fan units on and offline when a building control system requires a low volume of air atrelatively high pressure.
 23. The control system of claim 1, wherein thecontroller is configured to modulate the fan units on and off line toproduce a select operating point.
 24. The control system of claim 23,wherein the select operating point represents a stable operating point.25. The control system of claim 1, wherein the controller is configuredto modulate the fan units on and off to eliminate surge effects, wherethe surge effect occurs when a system pressure is too high for the fanspeed at a given volume and the fan units have a tendency to go intostall.
 26. The control system of claim 1, wherein the controller isconfigured to take off line a number of the fan units and speed upon-line fan units, to avoid a surge effect, where the surge effectoccurs when a system pressure is too high for the fan speed at a givenvolume and the fan units have a tendency to go into stall.
 27. Thecontrol system of claim 1, wherein the controller is configured tomodulate the fan units on and off line and control the speed of the fanunits that are on line to produce a stable operating point and avoidstall.
 28. A method for controlling an array of fan units having apreselected number of fan units, said fan units arranged in a fan array,said array capable of operation with a number of operative fan unitsless than the preselected number of fan units the method comprising:providing a controller calculating an operating level required tooperate the array at a selected static pressure and a selected airflowfor multiple different candidate numbers of operative fan units;identifying, from the multiple candidate numbers, one of the candidatenumbers of operative fan units that will achieve a desired operatinglevel while providing the selected static pressure and selected airflow;and turning fan units on or off until said identified one of thecandidate numbers of operative fan units is reached.
 29. The method ofclaim 28 wherein the controller calculates the operating level bycalculating a power level required using the equation${\sum\limits_{n = 0}^{X}\;{C_{n}{{CFM}^{n}\left( \frac{Df}{Ef} \right)}^{n - 1}\left( \frac{Ds}{Es} \right)^{n - 3}}},$where C_(n) are coefficients determined by system design, CFM is theairflow in cubic feet per minute, Df is the preselected number of fanunits in the system, Ef is number of operative fan units, which isiteratively incremented, Ds is a design maximum speed of the fan units,Es is an operating speed of the fans, which is iteratively incrementedand X is the total number of coefficients.
 30. The method of claim 29wherein the values of coefficients C_(n) are calculated by a methodcomprising the steps of: a. measuring the power level as a function ofairflow for a single fan unit; b. fitting the resulting data with apolynomial of order m, where m is an integer; c. setting the value ofC_(n) equal to the coefficient of the nth-power term of the fittedpolynomial for n running from zero to m; and d. setting X equal to m.31. The method of claim 28, wherein the controller calculates thecandidate numbers of operative fan units through an iterative feedbackcontrol loop.
 32. The method of claim 28 further comprising the step ofcalculating a fan unit speed required to provide a selected volume ofairflow at a selected static pressure for different numbers of operativefan units.
 33. The method of claim 32 wherein the results of the fanunit speed calculation are used in calculating power level.
 34. Themethod of claim 28 wherein the static pressure is given by the equation${\sum\limits_{n = 0}^{X}\;{C_{n}{{CFM}^{n}\left( \frac{Df}{Ef} \right)}^{n}\left( \frac{Ds}{Es} \right)^{n - 2}}},$where C_(n) are coefficients determined by system design, CFM is theairflow in cubic feet per minute, Df is the preselected number of fanunits in the system, Ef is the number of operative fan units, which isiteratively incremented, Ds is the design maximum speed of the fanunits, Es is an operating speed of the fans, which is iterativelyincremented, and X is the total number of coefficients.
 35. The methodof claim 34 wherein the values of coefficients C_(n) are calculated by amethod comprising the steps of: a. measuring an empirical staticpressure as a function of an empirical airflow for a single fan unit; b.fitting the resulting data with a polynomial of order m, where m is aninteger; c. setting the value of C_(n) equal to the coefficient of thenth-power term of the fitted polynomial for n running from zero to m;and d. setting X equal to m.
 36. The method of claim 28, wherein thecontroller calculates candidate numbers of operative fan unit units andfan unit speeds that satisfy programmed environmental parameters. 37.The method of claim 28 wherein the controller alters the number ofoperative fan units automatically.
 38. The method of claim 28, furthercomprising configuring the controller to permit a user to program thedesired operating level.
 39. The method of claim 28, further comprisingproviding the array of the preselected number of fan units.
 40. Themethod of claim 28, further comprising configuring the controller totake the fan units on and off line when a building control systemrequires a low volume of air at relatively high pressure.
 41. The methodof claim 28, further comprising modulating the fan units on and offline, at the direction of the controller, to produce a select operatingpoint.
 42. The method of claim 41, wherein the select operating pointrepresents a stable operating point.
 43. The method of claim 28, furthercomprising configuring the controller to modulate the fan units on andoff to eliminate surge effects, where the surge effect occurs when asystem pressure is too high for the fan speed at a given volume and thefan units have a tendency to go into stall.
 44. The method of claim 28,further comprising configuring the controller to take off line a numberof the fan units and speed up on-line fan units, to avoid a surgeeffect, where the surge effect occurs when a system pressure is too highfor the fan speed at a given volume and the fan units have a tendency togo into stall.
 45. The method of claim 28, further comprising modulatingthe fan units on and off line and control the speed of the fan unitsthat are on line to produce a stable operating point and avoid stall.46. An air handling system comprising: a. a preselected number of fanunits; b. said fan units arranged in a fan array, said array capable ofoperation with a number of operative fan units less than the preselectednumber of fan units; c. a controller calculating an operating levelrequired to operate the array at a selected static pressure and aselected airflow for each of multiple different candidate numbers ofoperative fan units, identifying from the multiple candidate numbers oneof the candidate numbers of operative fan units that will achieve adesired operating level while providing the selected static pressure andselected airflow, and turning fan units on or off until said identifiedone of the candidate numbers of operative fan units is reached.
 47. Theair handling system of claim 46, wherein the controller operates in afeedback control loop to maintain the fan units operating at the desiredoperating level.
 48. The air handling system of claim 46, wherein thecontroller calculates a necessary fan unit speed to give a selectedstatic pressure at a selected airflow for candidate numbers of operativefan units.
 49. The air handling system of claim 46, wherein thecontroller varies airflow and/or static pressure by varying a number ofoperative fan units as environmental parameters of a building change.50. The air handling system of claim 49, wherein the environmentalparameters for a building include at least one of airflow, humidity,temperature and static pressure.
 51. A method for controlling an arrayof fan units, comprising the steps of: a. providing a preselected numberof fan units, said fan units arranged in a fan array, said array capableof operation with a number of operative fan units less than thepreselected number of fan units; b. automatically calculating, at acontroller, multiple combinations of candidate fan unit speeds andnumbers of operative fan units configured to provide at least one of acommon select static pressure or common select airflow; c. automaticallyselecting, at the controller, from the multiple combinations, one of thecombinations of candidate fan unit speeds and number of operative fanunits so as to permit the operative fan units to run at a desired levelwhile providing the at least one of a common select static pressure orcommon select airflow.
 52. The method of claim 51, wherein thecontroller calculates the combinations by calculating a necessary fanunit speed to give a selected static pressure at a selected airflow forcandidate numbers of operative fan units.
 53. The method of claim 51,wherein the controller calculates the combinations by calculating apower level required to operate the fan array at a selected staticpressure, a selected airflow, and with different numbers of operativefan units, and then adjusting the number of operative fan units and aspeed of the fan units to achieve a desired power level.
 54. The methodof claim 51, wherein the controller alters the number of operative fanunits automatically.
 55. The method of claim 51, wherein the calculatingoperation is through an iterative feedback loop.
 56. The method of claim51, wherein the calculating operation calculates the combinationsthrough an iterative feedback control loop.
 57. The method of claim 51,wherein the calculating operation calculates the combinations ofcandidate fan unit speeds and numbers of operative fan units thatsatisfy programmed environmental parameters.
 58. The method of claim 51,wherein the selecting operation selects one of the combinations topermit the operative fan units to operate in a desired efficiency range.